I'm from what should probably be called the dark ages of hi-fi, when we would first judge amplifiers by their weight. My living room system is based around a giant 20kg (44lb) Pioneer receiver which was tested in its day to be capable of dynamic power of 280 Watts into 4 ohms (and 450 Watts into 2 ohms). Test report here:
http://www.milleraudioresearch.com/download/reports/aug04/pioneervsxax5i.html
This week, I started looking for a headphone amp for late night listening, became curious about what these mini amps could do, so ended up, with the help of this forum, with a SMSL C100 DAC, Aiyima A07 amp and a Sabaj A10h headphone amp, all for the princely sum of 215GBP. (The Sabaj is still on its way).
I started by going through the amplifier power requirement test here
http://archimago.blogspot.com/2017/09/musings-how-much-amplifier-power-do-you.html and worked out my real world power needs were well within the capabilities of the Aiyima A07 with its stock 32V 5A power supply.
My speakers are the Dynaudio Contour 1.3 mk2, a 25 year old high quality bookshelf design, 86db/2.83v/m sensitivity, said at the time to be fairly current hungry but a not particularly reactive load. Here are the impedance/phase measurements from its Stereophile test:
I am also using a Marantz PM66KIS amp which I recently got out of storage - this is rated at 70 wpc into 4 ohms but was tested to deliver 132. This was the amp I was using when I first bought the Dynaudio speakers. It, and the Pioneer receiver, drive them very nicely indeed. As does a Naim XS integrated amp which I have in my study, currently hooked up to some Tannoy dual concentrics.
So what do I think of the results? In a word, eye-opening for this old dinosaur. As predicted, the Aiyima drives the speakers to any level you could possibly want in my room, and I listen to a lot of classical music, so require a very high dynamic range. The sound is very clean, no noise audible in use - I turned the amp up to max gain with no music playing and pressed my ear against the tweeter and there was only a barely perceptible hiss (albeit with my old ears which hear nothing above 12khz). This is a big improvement over the aging Marantz - when I got it out of storage I had to open it up and clean the switch contacts inside (it's all mechanical) and it still crackles slightly with the same ear-to-tweeter test. More Importantly, the Marantz has a big toroidal transformer which buzzes randomly (not through the speakers, not level-dependant - presumably DC on the mains) - when it happens it can be heard even when wearing headphones. There's none of that with the Aiyima.
I've currently got the SMSL DAC connected to the Aiyima, with the amp's useful passthrough AUX out connected to the Marantz amp. I have a switch to allow the speakers to be switched from one amp to the other. I'm A-B testing, obviously not blind (though by tomorrow I might have forgotten which is which on the switch!), and it's the usual psychoacoustic story: Switch from one to the other and it sounds better. Then switch back and it sounds better still (how many times do you need to switch before it sounds better that the original performance?). More seriously, this tells me the A07 is very good indeed and I'm using it well within its capabilities even with the stock power supply.
When the Sabaj headphone amp arrives, I intend to connect the DAC directly to it, and drive the A07 from the Sabaj's line out, which as tested in this forum has a very high quality volume control, independently adjustable for the HP/line out, and with remote control. I could even connect an analogue source to the Aiyima AUX socket, If I wanted, just for fun. I'm looking forward to it.
